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THE  PLEISTOCENE  HISTORY  OF  THE 
LOWER  WISCONSIN  RIVER 


A  DISSERTATION 

SUBMITTED  TO   THE  FACULTY 

OF  THE  OGDEN  GRADUATE  SCHOOL  OF  SCIENCE 

IN  CANDIDACY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 

DEPARTMENT  OF  GEOLOGY 


BY 

PAUL  MAcCLINTOCK 


Private  Edition,  Distributed  By 

THE  UNIVERSITY  OF  CHICAGO  LIBRARIES 

CHICAGO,  ILLINOIS 


Reprinted  from 

THE  JOURNAL  OF  GEOLOGY,  Vol.  XXX,  No.  8 
November-December,  1922 


Ube  mntversttp  of  Gbicago 


THE  PLEISTOCENE  HISTORY  OF  THE 
LOWER  WISCONSIN  RIVER 


A  DISSERTATION 

SUBMITTED  TO   THE  FACULTY 

OF  THE  OGDEN  GRADUATE  SCHOOL  OF  SCIENCE 

IN  CANDIDACY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 

DEPARTMENT  OF  GEOLOGY 


BY 

PAUL  MAcCLINTOCK 


Private  Edition,  Distributed  By 

THE  UNIVERSITY  OF  CHICAGO  LIBRARIES 

CHICAGO,  ILLINOIS 


Reprinted  from 

THE  JOURNAL  OF  GEOLOGY,  Vol.  XXX,  No.  8 
November-December,  1922 


v 


EARTH 

SCIENCES 

LIBRARY 


EXCHANGE 


THE  PLEISTOCENE  HISTORY  OF  THE  LOWER 
WISCONSIN  RIVER1 


PAUL  MACCLINTOCK 

University  of  Chicago 


INTRODUCTION 

The  Wisconsin  River,  rising  among  the  glacial  lakes  in  the 
northern  part  of  the  state  of  Wisconsin,  flows  almost  due  south 
nearly  to  Portage,  where  it  turns  and  flowing  westward  for  a  dis- 
tance of  about  80  miles  joins  the  Mississippi  just  south  of  Prairie 
du  Chien  (Fig.  i).  It  is  this  lower,  east- west  part  of  the  river 
valley  which  is  discussed  in  this  paper.  The  terminal  moraine  of 
the  Wisconsin  glacial  epoch  crosses  the  valley  just  east  of  Prairie 
du  Sac  and  marks  not  only  the  eastern  boundary  of  the  region  here 
considered  but  also  that  of  the  drif tless  area.  Since  glacial  drift  is 
found  in  Iowa  opposite  the  lower  end  of  the  valley,  it  may  be  said 
that  the  Wisconsin  River  traverses  from  east  to  west  the  entire 
driftless  area.  It  is  thus  seen  that  drift  remnants  which  are  found 
in  this  part  of  the  valley  are  of  important  significance  in  the  history 
of  ancient  ice  invasions  in  bordering  regions. 

These  remnants  of  glacial  drift  in  the  valley  fall  naturally  into 
two  divisions:  First,  there  are  terraces  of  Wisconsin  age:  (a) 
remnants  of  the  valley  train  sloping  from  the  terminal  moraine, 
where  it  crosses  the  valley  near  Prairie  du  Sac,  to  the  Mississippi 
River,  and  (b)  a  lower  terrace  standing  only  15  feet  above  the  pres- 
ent river  flood-plain;  and  second,  standing  well  above  the  preced- 
ing terrace,  are  rock  benches  covered  with  much  older  drift.  These 
upper  benches  have  a  gentle  slope  toward  the  east  (Fig.  2). 

PART  I.      OLDER  DRIFT 

Stated  in  the  simplest  terms,  there  are  six  areas  of  the  older 
drift:  (i)  near  Lone  Rock,  (2)  near  Muscoda,  (3)  from  Muscoda 
to  Boscobel,  (4)  from  Boydtown  to  the  Kickapoo  River,  (5)  at 

1  Condensed  from  Ph.D.  thesis  submitted  to  the  Department  of  Geology,  the 
University  of  Chicago,  1920. 

673 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER    675 


Wauzeka,  (6)  at  Bridgeport.  The  first  four  of  these  are  similar 
in  topography,  constitution,  and  amount  of  weathering,  while  the 
last  two  differ  from  the  others  in  that  they  contain  not  only  much 
striated  material  (at  Bridgeport)  but  also  a  large  percentage  of 
calcareous  material. 


I.      SUBDIVISION 


It  appears  from  the  evidence  that  the  older  drift  is  not  all  of  the 
same  origin  or  age. 

a)  A  lithologic  study  of  some  300  characteristic  rock  specimens 
collected  from  the  different  exposures,  and  examined  in  the  labora- 
tory, shows  37  common  to  Wauzeka  and  Bridgeport,  17  common  to 


i 


i 


-  '     :•  ' 


.........  Older  Ttmctt 

Lou   W Itcwtn   Ten 


FIG.  2. — Profile  of  the  Wisconsin  River  Valley  from  Prairie  du  Sac  to  Prairie 
du  Chien  showing  the  bedrock,  the  drift  partly  filling  the  valley,  and  the  levels  of 
the  three  terraces. 

Orion  (Port  Andrew)  and  the  nearest  Illinoian  drift  at  Verona, 
9  miles  southwest  of  Madison,  27  common  to  Orion  and  Wauzeka, 
and  25  common  to  Bridgeport  and  Iowa  (near  McGregor).  These 
facts  show  that  there  is  close  similarity  between  the  drifts  of  Illi- 
noian age  and  that  at  Orion  on  the  one  hand,  and  between  the 
drift  at  Wauzeka,  Bridgeport,  and  Iowa  on  the  other. 

b)  The  drift  at  Wauzeka  and  Bridgeport  contains  much  lime- 
stone and  dolomite,  while  farther  up  the  valley  there  is  neither. 
Since  the  Illinoian  and  pre-Illinoian  drifts  east  of  the  region  contain 
calcareous  material,  it  is  likely  that  these  terrace  deposits  in  the 
mid-course  of  the  valley  originally  contained  the  carbonates  which 
have  been  subsequently  leached. 


676 


PAUL  MACCLINTOCK 


c)  There  is  well-developed  cross-bedding  at  Blue  River  dipping 
westward,  while  at  Wauzeka,  less  well-developed  but  still  recog- 
nizable cross-bedding  in  sandy  layers  dips  eastward  (Fig.  3). 

d)  While  there  are  numerous  bowlders  in  the  drift  of  the  mid- 
course  of  the  valley,  there  are  more  to  be  seen  at  Wauzeka  and 
Bridgeport. 


FIG.  3.- 
Blue  River. 


-Westward  dipping  gravel  on  the  high  terrace  two  miles  northeast  of 


e)  On  the  Bridgeport  terrace  the  stones  are  not  only  more  angu- 
lar than  elsewhere  in  the  valley,  but  numerous  subangular  and 
striated  ones  are  found.  In  fact  these  glaciated  stones  are  as 
numerous  on  this  terrace  as  in  the  till  either  in  Iowa  or  at  the 
eastern  end  of  the  region. 

The  suggestion  from  this  evidence  is  that  the  drift  in  the  mid- 
course  of  the  valley  is  fluvio-glacial  and  from  the  east,  while  that 
at  Bridgeport  is  glacial,  and  that  at  Wauzeka  is  fluvio-glacial  and 
both  the  latter  are  from  the  west. 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER   677 

2.      MID-COURSE  DRIFT 

a)  Origin. — The  cross-bedding  at  Blue  River  makes  it  evident 
that  the  drift  in  the  mid- course  was  brought  in  from  the  east 
(Fig.  3).     This  being  the  case,  the  upper  surface  of  these  terrace 
deposits  should  slope  conspicuously  toward  the  west,  for,  while 
large  bowlders  so  common  in  most  of  the  exposures  may  have  been 
carried  in  bergs,  the  mass  of  the  material  is  fluvial  and  must  have 
been  transported  by  a  glacial  river — a  river  having  powerful  current 
and  fairly  steep  gradient.     A  steep  gradient  may  well  be  postulated 
for  such  a  glacial  river,  for  there  appears,  if  the  bedrock  floor  of 
the  valley  be  considered,  to  have  been  down-warping  at  the  eastern 
end  of  the  region.     The  bedrock  in  the  valley  bottom  near  Prairie 
du  Sac  has  an  altitude  of  something  less  than  500  feet,1  while  at 
Prairie  du  Chien,  near  the  mouth,  its  altitude  is  490  feet,  making 
a  gradient  of  only  two  inches  to  the  mile  (Fig.  2).     The  preglacial 
river  with  so  low  a  gradient  as  this  could  not  have  eroded  so  deep 
and  narrow  a  valley  as  the  rock  bottom  of  this  part  of  the  Wis- 
consin Valley  appears  to  be.     The  unavoidable  inference  is  that  the 
eastern  end  of  the  region  must  have  been  higher  in  preglacial  and 
possibly  early  glacial  times,  and  must  have  subsided  before  the  last 
glacial  advance.     Data  from  neighboring  regions  also  suggest  that 
such  warping  has  taken  place.2 

b)  Age. — Old  drift  has  been  described  on  the  eastern  margin 
of  the  driftless  area  by  Leverett,  Weidman,  and  Alden,3  and  called 
by  them  pre-Illinoian  in  age.     The  absence  of  calcareous  material  in 
the  old  drift  in  the  mid-course  of  the  Wisconsin  Valley,  even  where 
seen  10  and  12  feet  below  the  surface,  suggests  that  it  is  as  old  as 
Kansan  and  probably  older,  i.e.,  the  outwash  from  the  first  ice 
advance. 

3.      WESTERN  DRIFT 

a)  Origin. — The  drift  on  the  Bridgeport  terrace  must  be  either 
glacial  or  fluvio-glacial  in  origin.     The  large  number  of  striated  and 

'  W.  C.  Alden,  U.S.  Geol.  Surv.  Prof.  Paper  106  (1918),  Plate  II. 

2  W.  C.  Alden,  op.  tit.;  F.  Leverett,  Journal  of  Geology,  Vol.  Ill  (1895),  p.  740; 
E.  W.  Shaw,  Butt.  Geol.  Soc.  Amer.,  Vol.  XXVI  (1914),  P-  67. 

3  F.  Leverett,  U.S.  Geol.  Surv.  Monograph  38  (1899),  pp.  109-10;    S.  Weidman, 
Wis.  Geol.  Surv.,  Bull.  16  (1907),  p.  433;  W.  C.  Alden,  op.  tit.,  p.  168. 


678  PAUL  MACCLINTOCK 

subangular  stones  found  nowhere  else  in  the  outwash  material  of 
the  valley,  together  with  the  patchy  character  of  the  drift,  suggests 
deposition  directly  by  the  ice.  If  this  view  is  correct  the  glacier 
must  have  extended  from  Iowa  across  the  Mississippi  into  the 
lower  end  of  the  Wisconsin  Valley. 

On  the  other  hand,  at  no  place  where  this  older  drift  occurs  was 
a  glacial  pavement  seen.  The  drift  lies  in  most  places  on  deeply 
eroded  and  weathered  dolomite,  while  at  other  places  several  inches 
of  blue-black  clay,  weathered  from  the  bedrock,  lies  at  the  base  of 
the  brown  drift.  It  is  not  strange  that,  in  exposures  so  limited, 
no  pavement  was  seen;  none  has  been  found  in  Iowa  in  this  vicinity, 
where  the  ice  is  known  to  have  stood  to  the  very  edge  of  the  Miss- 
issippi Valley.  It  seems  probable  that  if  a  tongue  of  ice  projected 
into  the  Wisconsin  Valley  for  a  distance  of  4  miles — -a  condition 
called  for  by  this  hypothesis — it  would  have  been  at  least  as  wide  as 
the  mouth  of  the  valley  (if  miles)  so  that  its  shoulders  would 
have  rested  against  the  valley  walls  near  the  mouth,  and  have  left 
there  glacial  material.  Some  material  of  this  kind  is  seen  for  a 
distance  of  if  miles  north  of  the  lower  end  of  the  Wisconsin  Valley. 
It  is  however  small  in  size,  meager  in  quantity,  and  found  not  strictly 
on  the  shoulders  but  on  the  lower  slopes  at  heights  of  never  more 
than  100  feet  above  the  flood-plain.  Glacial  material  on  slopes  so 
steep  as  the  shoulders  present  would  not  have  remained  there  but 
would  have  soon  been  washed  to  the  flat  below. 

The  crucial  points  are:  (i)  the  Bridgeport  drift  is  much  higher 
in  altitude  than  any  of  the  •  older  drift  farther  up  the  valley, 
(2)  it  is  composed  of  striated,  subangular,  and  grooved  material, 
and  (3)  it  is  both  stratified  and  unstratified — the  latter  material 
indistinguishable  from  till.  The  conclusion  then  is  that  this  drift 
is  glacial  in  origin  and  was  deposited  by  a  tongue  of  ice.  It  seems 
clear  that  the  drift  at  Wauzeka  is  the  outwash  material  from  the 
same  ice  invasion,  for  it  is  closely  akin  to  the  Bridgeport  drift  in 
many  ways,  has  the  lense  and  pocked  structure  of  outwash  material, 
and  has  a  suggestion  of  eastward  dipping  cross-bedding  (Fig.  4). 
None  of  this  calcareous  drift  is  found  farther  up  the  valley  because 
the  decline  of  this  old  valley  train  would  have  brought  its  top 
below  the  level  of  the  rock  benches  where  drift  is  now  found. 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER    679 

This  hypothesis  involves  a  damming  of  the  Mississippi  River 
by  the  ice  tongue  at  the  mouth  of  the  Wisconsin.  Under  this 
condition  the  Mississippi  must  then  have  flowed  between  this  ice 
tongue  and  the  northern  wall  of  the  Wisconsin  Valley  and  thence 
eastward  to  the  Rock  River  or  more  probably  the  Lake  Michigan 
Basin.  Such  an  eastward  flowing  river,  if  the  bedrock  divide 
near  Portage  had  about  the  present  altitude  of  600  feet,1  would  have 


FIG.  4. — View  of  the  outwash  material  on  the  high  terrace  at  Wauzeka  showing 
lenses  of  sand  in  the  gravel. 

had  a  gradient  of  about  2.5  feet  per  mile,  or  a  foot  per  mile  greater 
than  that  of  the  present  Wisconsin  River.  This  suggests  that  the 
down-warping  of  the  eastern  part  of  the  area,  mentioned  above,  had 
already  taken  place.  It  seems,  in  fact,  quite  probable  that  this 
eastern  part  of  the  region  was  lower  than  it  is  at  present,  for  post- 
Champlainic  uplift  and  warping  in  the  Great  Lakes  area  probably 
raised  the  divide  from  some  lower  elevation  to  its  present  altitude. 
Since  such  down-warping  as  first  mentioned  has  been  found  in 

1  W.  C.  Alden,  op.  cit.,  Plate  II. 


680  PAUL  MACCLINTOCK 

neighboring  regions,  it  seems  well  to  note  it  here,  and  by  so  doing 
possibly  to  fix  the  date  of  the  warping — after  the  first  ice  invasion 
at  the  east  of  the  area  and  before  the  second  invasion  on  the  west. 

Additional  evidence  of  such  a  displacement  of  the  Mississippi 
might  be  expected  in  old  channels.  In  the  eastern  part  of  the 
valley,  Wisconsin  glaciation  has  destroyed  any  possible  trace, 
while  at  the  west  the  river  was  either  displaced  for  so  short  a  time, 
or  subsequent  erosion  has  been  so  great  that  there  is  no  evidence 
of  a  channel  occupied  during  the  displacement.  No  channel  is  found 
in  Jo  Daviess  County,  Illinois,  where  a  similar  tongue  of  ice  pushed 
across  the  Mississippi  Valley  from  Iowa  and  left  drift  near  Hanover.1 

b)  Age. — Two  drift  sheets,  the  Kansan  and  the  pre-Kansan, 
are  thought  to  be  present  in  Iowa  near  the  mouth  of  the  Wiscon- 
sin River.2  The  western  drift  in  the  Wisconsin  Valley  must  be 
correlated  in  age  with  one  of  these.  The  former  drift  sheet  is  less 
weathered  than  the  latter,  which  is  represented,  according  to  present 
determinations,  only  by  scattered  and  very  much  weathered  errat- 
ics. Judging  from  the  thickness  (20  to  50  feet),  and  from  the  large 
content  of  limestone  and  dolomite,  it  seems  most  probable  that 
the  Bridgeport  and  Wauzeka  drift  is  of  Kansan  age. 

PART  H.      WISCONSIN  DRIFT 

i.  The  terminal  moraine  of  the  last  glacial  invasion  extends 
southward  from  the  Baraboo  Range,  crossing  the  Wisconsin  River 
i£  miles  northeast  of  Prairie  du  Sac.  On  the  south  side  of  the 
river  it  maintains  a  southerly  direction  to  Black  Earth  Creek  which 
it  crosses  i  J  miles  east  of  Cross  Plains.  North  of  the  river  this 
moraine  is  a  belt  showing  morainic  topography,  while  south  of  the 
river  it  is  in  most  places  a  narrow  distinct  ridge  strewn  with 
bowlders.  Where  it  crosses  the  river  the  section  shows  60  feet  of 
cross-bedded  sand  with  small  lense?  of  fine  gravel,  overlain,  with 
a  sharp  contact,  by  30  feet  of  till.  The  sharp  contact  shows  no 
weathering.  This  sand  may  be  outwash  from  an  early  Wisconsin 
moraine  farther  east  or  may  be  the  outwash  deposited  in  front  of 
the  advancing  late  Wisconsin  ice. 

1 E.  W.  Shaw  and  A.  C.  Trowbridge,  ///.  State  Geol.  Surv.  Bull.  26  (1916),  p.  87. 
a  A.  C.  Trowbridge,  Bull  Geol.  Soc.  America,  Vol.  XXVI  (1914),  p.  76. 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER    681 

2.  Sloping  gently  westward  from  the  moraine  north  of  the  river 
a  sandy  outwash  plain  extends  to  an  irregular  boundary  against 
the  sandstone  hills  of  the  country  rock.     The  western  edge  is  irreg- 
ular, for  the  nuvio-glacial  material  is  found  up  the  valleys  of  Honey 
and  Otter  creeks.     Of  special  interest  are  the  erratics  found  in 
the  south  branch  of  Honey  Creek  as  far  west  as  Blackhawk  and 
Plain.     They  lie  on  an  upper  terrace,  corresponding  in  elevation 
to  that  of  the  outwash  plain  across  the  mouth  of  the  creek  at  its 
eastern  end.     This  position,  17  miles  beyond  the  terminal  moraine, 
implies  that  the  bowlders  were  carried  to  their  positions  while 
frozen  in  blocks  of  ice  floating  on  a  lake. 

Such  a  lake  may  have  been  formed  in  one  of  two  ways: 

a)  The  edge  of  the  ice  may  have  extended  beyond  the  terminal 
moraine  and  dammed  the  mouth  of  Honey  Creek.    No  evidence 
was  found  to  substantiate  this  possibility. 

b)  As  the  outwash  plain  was  being  built,  the  glacial  waters 
issuing  from  the  ice-front  between  Prairie  du  Sac  and  the  South 
Range  swept  their  load  southward  across  the  mouth  of  Honey 
Creek.     Outwash  material  may  thus  have  dammed  the  mouth  of 
Honey  Creek,  forming  a  lake  upon  which'icebergs  may  have  floated 
the  bowlders.    While  this  suggestion  involves  the  difficulty  of 
getting  the  bergs  swept  across  the  outwash  plain  and  into  the  lake, 
it  still  seems  the  more  probable  of  the  two. 

3.  The  valley  train,  now  represented  by  terrace  remnants,  once 
filled  the  bottom  of  the  valley  from  the  terminal  moraine  to  the 
Mississippi  River.     It  was  90  feet  above  the  present  flood-plain 
near  the  terminal  moraine,  30  feet  in  mid-course,  and  40  feet  at 
the  western  end  of  the  valley.    As  this  outwash  deposit  was  grow- 
ing, the  glacial  waters  constantly  deposited  material  across  the 
mouths  of  the  tributary  valleys,  causing  them  in  turn  to  aggrade 
their  channels.    Terrace  remnants  of  these  slack-water  deposits  are 
to  be  seen  in  most  of  the  tributary  valleys,  serving  to  project  the 
level  of  the  valley  train  even  where  it  has  been  removed  from  the 
main  valley  by  subsequent  erosion. 

The  most  easterly  remnant  of  the  original  valley  train  lies  near 
Mazomanie  at  the  mouth  of  Black  Earth  Creek.  It  is  an  irregular 
area  a  mile  wide  by  6  miles  long,  separated  from  the  south  bluffs 


682  PAUL  MACCLINTOCK 

by  Black  Earth  and  Halfway  Prairie  creeks.  The  surface  of  this 
area  is  gently  rolling  and  marked  here  and  there  by  patches  of  low 
sand  dunes.  This  terrace  level  extends  eastward  into  Black  Earth 
and  Halfway  Prairie  valleys  while  the  two  intervening  shorter 
valleys  have  this  high  fill  only  at  their  very  mouths.  This  relation- 
ship is  of  importance  in  connection  with  the  problem,  later  to  be 
considered,  of  the  age  of  the  terrace. 

From  Mazomanie  for  a  distance  of  30  miles  to  the  west,  the 
upper  part  of  the  valley  train  has  been  entirely  removed  from  the 
main  valley.  The  terrace  level  is,  however,  present  in  most  of  the 
tributary  valleys;  notably  Blue  Mounds,  Wyoming,  Otter,  Pine, 
Eagle,  and  Kickapoo  creeks.  But  there  are  several  tributary 
valleys  (see  Fig.  i)  lacking  this  terrace  level,  a  fact  whose  signifi- 
cance is  later  to  be  considered. 

The  remnants  of  this  level,  the  high  Wisconsin  terrace,  are 
again  found  in  the  main  valley  near  Muscoda  and  Blue  River  where 
the  bench  is  protected  by  a  subjacent  ledge  of  sandstone  against 
which  the  river  is  at  several  places  flowing.  At  Boscobel  a  large 
terrace  remnant  lies  against  the  south  wall  of  the  valley.  In  these 
latter  terrace  patches  the  material  is  smaller  in  size  and  contains 
fewer  limestone  pebbles  than  farther  up  the  valley. 

4.  Twelve  to  15  feet  above  the  Wisconsin  River  flood-plain  and 
extending  short  distances  up  the  valleys  of  many  of  its  tributaries 
there  is  an  extensive  sandy  terrace — the  low  Wisconsin  terrace. 
From  the  terminal  moraine  at  Prairie  du  Sac  to  Wauzeka,  a  distance 
of  65  to  70  miles,  it  is  nearly  continuous  in  the  main  valley  on  one 
side  of  the  river  or  the  other,  while  from  Wauzeka  to  the  Mississippi 
it  occurs  only  in  small  detached  areas.  Remarkable  uniformity  in 
height  above  the  river  is  one  of  its  most  notable  characteristics,  for 
the  variation  is  not  more  than  a  foot  or  two  throughout  the  whole 
distance.  A  second  notable  feature  is  that  the  material,  where 
seen  in  shallow  cuts,  is  uniform  in  size  and  constitution  through 
the  whole  length  of  the  valley,  being  mostly  sand  with  small  pebbles 
scattered  rather  uniformly  through  the  mass.  The  surface  of  this 
terrace  is  in  general  very  flat,  but  in  detail  it  is  seen  to  have  irregu- 
larities produced  by  the  wind,  such  as  sand  dunes  and  "  blow- 
holes." Considerable  dune  areas  are  found  in  the  neighborhood 
of  Lone  Rock  and  Spring  Green.  In  fact,  the  whole  terrace  is  so 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER   683 

sandy  and  so  poor  as  farm  land  that  it  is  called  locally  " Prairie" 
or  " Barrens." 

There  are  three  possibilities  to  be  considered  in  discussing  the 
origin  of  the  low  terrace:  It  is  either  the  valley  train  of  the  late 
Wisconsin  ice  advance  or  was  cut  from  the  early  Wisconsin  valley 
train  by  waters  from  a  glacial  lake,  or  is  a  combination  of  the  two. 


FIG.  5 — Diagram  showing  the  relation  of  the  terraces  in  the  four  valleys  east  of 
Mazomanie.  Black  Earth  and  Halfway  Prairie  creeks  contain  the  high  terrace  while 
the  two  shorter  valleys  do  not. 

a)  Alden  is  of  the  opinion  that  the  low  terrace  is  the  result  of 
deposition  by  glacial  waters  from  the  late  Wisconsin  invasion,  while 
the  upper  terrace  resulted  from  the  early  Wisconsin  advance.1  The 
evidence  is  as  follows:  Of  the  four  small  valleys  east  of  Mazomanie, 
the  two  longer  ones  contain  the  upper  terrace  while  the  shorter 
ones  do  not.2  This,  Alden  interprets  as  meaning  that  the  ice  of 
the  early  Wisconsin  invasion  did  not  reach  the  heads  of  the  shorter 
valleys,  discharging  its  waters  only  through  the  longer  ones  and 
building  in  them  the  high  terrace  (Fig.  5). 

1  W.  C.  Alden,  op.  cit.,  pp.  191-93  and  244-45. 

a  The  northern  one  does  contain  several  small  patches  (see  Fig.  5). 


684  PAUL  MACCLINTOCK 

Following  the  retreat  of  the  early  Wisconsin  ice  came  a  period 
of  erosion  during  which  part  of  the  fill  was  cut  away.  The  late 
Wisconsin  ice  advanced  farther  and  stood  across  the  heads  of  all 
four  valleys,  building  valley  trains  at  the  level  of  the  low  terrace. 
At  the  same  time  the  low  terrace  was  being  built  in  the  main  valley. 

Evidence  adverse  to  this  suggestion  must  be  summarized  under 
several  heads : 

i)  If  deposited  by  glacial  waters,  the  terrace  should  decline 
westward  more  rapidly  than  the  present  river,  unless  the  western 
end  had  been  raised  by  postglacial  tilting.  But,  judging  from  the 
tilting  of  the  glacial  beaches  of  the  Great  Lakes,  this  latter  possibility 
is  unlikely. 

if)  If  deposited  by  glacial  waters  the  material  should  be  notice- 
ably coarser  at  the  eastern  end  grading  to  fine  at  the  west.  This 
is  not  the  case. 

iif)  There  are  three  conspicuous  examples  of  small  valleys 
containing  only  the  low  terrace,  west  of  the  farthest  ice  advance 
(just  west  of  Black  Earth,  south  of  Arena,  and  west  of  Avoca), 
while  there  are  but  two  such  cases  among  the  valleys  heading  in 
the  terminal  moraine,  as  previously  cited.  It  would  seem  that 
the  mere  fact  that  two  of  the  four  valleys  east  of  Mazomanie  do 
not  have  the  high  terrace  is  not  conclusive  one  way  or  the  other. 
In  fact,  it  would  be  just  as  plausible  to  suppose  that  there  was  but 
one  Wisconsin  advance  in  this  region  and  that,  since  the  longer 
valleys  drained  the  ice  both  earlier  and  later  than  did  the  shorter 
ones,  they  received  more  outwash,  and  so  were  more  aggraded. 
The  thin  terminal  moraine  crossing  the  valleys  means  a  short  stay 
of  the  ice-edge  at  this  place,  or  poverty  of  debris  in  the  glacier. 

iv)  No  evidence  was  seen  of  weathering  of  the  stratified  drift 
underlying  the  till  of  the  terminal  moraine,  as  would  be  expected 
somewhere  in  the  region  if  it  were  early  Wisconsin  and  the  till  were 
late  Wisconsin,  since  this  interglacial  interval  is  considered  by  many 
to  be  fairly  long.  The  stratified  drift  may  as  well  be  outwash  depos- 
ited by  waters  which  flowed  out  in  advance  of  the  oncoming  ice. 

v)  The  evidence  from  the  larger  amount  of  leaching  of  the  out- 
wash  plain,  suggested  by  Alden  and  Weidman,1  as  showing  that 

1 W.  C.  Alden,  op.  cit.,  p.  192. 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER  685 

the  high  terrace  is  older  than  the  terminal  moraine  and  outwash  of 
the  low  terrace,  was  not  verified.  For  cuts  on  and  directly  west  of 
the  moraine  show  about  the  same  amount  of  leaching  as  do  the 
exposures  farther  west  on  the  high  fill. 

w)  The  high  terrace  marks  a  time  of  great  filling,  while  the 
low  one  is  much  less  important  in  this  respect.  Evidence  from 
other  regions  has  led  to  the  generalization  that  the  ice  of  the  late 
Wisconsin  substage  was  the  most  energetic  of  all  the  ice  advances, 
building  higher  and  more  rugged  moraines;  eroding  more  deeply 
and  more  conspicuously;  dumping  more  sediment  into  the  drainage 
lines  leading  away  from  the  ice-front,  and  so  building  larger  valley 
trains.  This  line  of  evidence  would  point  rather  to  the  late  Wisconsin 
than  the  early  Wisconsin  substage  as  the  builder  of  the  high  terrace. 

mi)  Since  erratics  in  Honey  Creek  Valley  rest  only  on  the  high 
Wisconsin  terrace,  it  seems  clear  that  a  glacial  lake  stood  in  this 
valley  during  at  least  part  of  the  time  when  the  slack-water  fill  of 
which  these  terraces  are  remnants  was  being  deposited.  It  would  be 
inferred  that  the  lake  was  dammed  during  the  maximum  extent  of 
the  ice,  rather  than  when  the  ice-edge  stood  farther  east,  as  it  did 
in  early  Wisconsin  time  if  the  early  Wisconsin  ice  affected  this 
immediate  region.  This  piece  of  evidence  suggests  that  the  high 
Wisconsin  fill  in  Honey  Creek  Valley  was  deposited  when  the  ice- 
front  stood  at  least  as  far  west  as  Prairie  du  Sac. 

The  weight  of  this  evidence  is  seriously  against  the  possibility 
that  the  low  terrace  was  deposited  as  a  valley  train  of  the  late 
Wisconsin  invasion. 

b)  When  the  ice-front  of  the  Green  Bay  lobe  had  withdrawn  east 
of  the  Portage  divide,  the  ice-dammed  lake,  Jean  Nicolet,1  was 
formed  with  its  outlet  down  the  Wisconsin  Valley.  These  outlet 
waters  were  clear,  and  probably  cut  the  upper  part  of  the  valley 
train  down  to  the  level  of  the  low  terrace.  Evidence  that  the  low 
terrace  was  cut  by  waters  from  Lake  Jean  Nicolet  follows. 

i)  The  uniform  height,  12  to  15  feet,  of  the  terrace  above  the 
flood-plain  all  the  way  from  the  terminal  moraine  to  the  mouth  of 
the  valley,  suggests  strongly  an  erosional  rather  than  a  depositional 
origin. 

1  W.  Upham,  Amer.  Geologist,  Vol.  XXXII  (1903),  P-  33°- 


686  PAUL  MACCLINTOCK 

ii)  The  material,  in  at  least  the  upper  few  feet  of  the  terrace, 
throughout  the  length  of  the  valley  is  uniform  in  size,  shape,  and 
structure.  The  river  having  a  uniform  gradient  would  handle 
sediment  of  uniform  size  through  its  whole  length.  This  would 
result  in  the  coarser  material  in  the  eastern  part  of  the  high  terrace, 
when  cut  by  these  outlet  waters,  being  buried  below  several  feet 
of  finer  re-worked  material  covering  the  low  terrace. 

Hi)  Its  similarity  to  the  Brule-St.  Croix  outlet  of  Lake  Duluth 
is  noticeable.  This  latter  is  also  a  broad  sandy  plain  with  dunes 
and  blowholes  upon  its  surface.1 

iv)  The  low  gradient,  1.75  feet  per  mile,  for  so  large  a  volume  of 
water,  would  favor  a  wide  rather  than  a  deep  cut. 

Against  this  mode  of  origin  the  following  points  may  be 
registered : 

i)  It  would  be  expected  that  the  upper  few  feet  of  the  terrace 
would  be  re-worked  by  the  running  water  and  the  material  therefor 
assorted.  But  this  is,  as  a  rule,  not  the  case,  for  the  pebbles  are 
scattered  indiscriminately  through  the  sand. 

ii)  Weidman  states,  in  relation  to  the  Brule-St.  Croix  outlet 
that  ".  .  .  .  Aside  from  cutting  down  a  few  drift  dams  that  lay 
across  the  outlet,  there  was  not  much  erosion."2  It  is  possible, 
then,  that  there  was  not  enough  cutting  by  the  waters  of  Lake 
Jean  Nicolet  to  cut  the  upper  terrace  to  the  level  of  the  lower  one. 
However,  the  rapidity  of  cutting,  depending  upon  the  volume  and 
the  velocity  of  the  river  as  well  as  the  kind  of  material  cut,  may 
not  have  been  the  same  in  the  two  cases.  So  the  slight  amount  of 
cutting  of  the  Brule-St.  Croix  outlet  would  not  carry  a  necessary 
implication  against  great  cutting  in  the  Wisconsin  Valley. 

Hi)  The  relation  of  the  terraces  in  the  four  tributary  valleys 
just  east  of  Mazomanie,  previously  discussed,  is  significant  but  not 
conclusive. 

From  the  weight  of  this  evidence,  the  low  terrace  appears  to  be 
a  degradational  level  cut  by  waters  from  the  glacial  lake. 

c)  A  third  suggestion  presents  itself  which  combines  the  first 
and  second  in  such  a  way  as  to  obviate  many  of  the  difficulties 

1  Moses  Strong,  Geology  of  Wisconsin,  Vol.  Ill  (1880),  p.  387. 
a  Samuel  Weidman,  personal  communication. 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER   687 

inhering  in  each.  With  the  advance  of  the  early  Wisconsin  stage, 
the  outwash  valley  train  was  deposited.  During  the  subsequent 
period  of  ice  withdrawal,  the  pounded  waters  of  the  Fox  River 
Valley  flowed  across  the  Portage  divide  and  down  the  Wisconsin 
Valley,  cutting  away  a  large  part  of  the  valley  train.  This  period 
must  have  been  rather  long,  or  erosion  excessively  rapid  by  a  large 
and  powerful  river,  for  more  erosion  took  place  then  than  has  taken 
place  since  the  last  withdrawal  of  the  ice.  This  would  not  appear 
to  be  improbable,  for,  during  this  partial  withdrawal,  the  ice  may 
have  dammed  the  lake  for  a  much  longer  period  of  time  than  it  did 
in  the  final  deglaciation.  Then  when  the  late  Wisconsin  ice 
advanced  to  the  region  of  Prairie  du  Sac,  the  outwash  partially 
filled  the  channel  cut  below  the  early  fill.  Later,  as  the  ice  with- 
drew, the  lake  was  again  dammed  east  of  the  Portage  divide 
and  the  waters  flowed  westward  down  the  Wisconsin  Valley,  cutting 
the  lower  fill  to  the  level  of  the  low  terrace.  This  would  involve 
less  cutting  at  any  one  stage  than  the  first  suggestion,  and  at  the 
same  time  would  allow  the  terrace  to  stand,  as  it  does,  at  a  con- 
stant elevation  above  the  present  river  level,  for  the  waters  from 
the  lake  probably  would  cut  to  the  same  gradient  as  do  those  of 
the  present  Wisconsin  River. 

While  the  hypothesis  of  two  Wisconsin  advances  will  explain 
the  presence  of  the  high  terrace  in  two  of  the  valleys  east  of  Mazom- 
anie  and  its  absence  from  the  other  two,  it  will  not  account  for 
the  absence  of  this  high  terrace  in  the  tributaries  farther  down  the 
Wisconsin  River.  And  since  it  is  evident  that  the  former  case  can 
be  explained  on  the  basis  of  one  advance  into  this  region,  the  idea 
of  two  ice  invasions  in  Wisconsin  time  may  be  discarded  as  needless. 

SUMMARY 

The  terraces  of  Wisconsin  age  may  be  best  explained  on  the 
hypothesis  that  they  are  connected  with  one  glacial  advance — that 
of  the  late  Wisconsin  ice-sheet — and  that  the  lower  terrace  was  cut 
from  the  higher  by  waters  issuing  from  Lake  Jean  Nicolet. 

PART   III.      THE   PLEISTOCENE   HISTORY 

The  first  glacial  invasion  in  Pleistocene  time  advanced  on  the 
eastern  side  of  the  region  to  a  position  somewhat  east  of  the  Wiscon- 


688  PAUL  MACCLINTOCK 

sin  terminal  moraine.  The  eastern  end  of  the  region  at  this  time 
stood  relatively  higher  than  it  does  now,  so  that  the  glacial  waters 
flowing  down  the  Wisconsin  Valley  had  a  steep  gradient  and  trans- 
ported coarse  debris.  The  glacial  drainage  from  at  least  a  hundred 
miles  of  ice-front  to  the  north  must  have  flowed  southward  to  the 
vicinity  of  Portage,  and  then  westward  down  the  Wisconsin  River. 
In  its  course,  along  the  ice  margin,  the  river  must  have  cut  against 
the  edge  of  the  ice,  at  least  in  places,  and  must  have  broken  off 
blocks  of  debris-laden  ice,  floating  them  into  the  Wisconsin  Valley. 
Here  many  of  them  must  have  grounded  and,  upon  melting,  have 
deposited  their  loads.  The  adequate  source  of  bergs,  the  abundant 
supply  of  glacial  material,  and  the  swift  and  powerful  glacial  river 
seem  sufficient  to  account  for  the  older  drift  deposited  on  the  terraces 
of  the  mid-course  of  the  valley.  After  the  ice  had  stood  long  enough 
to  build  a  valley  train  to  a  height  of  at  least  75  feet  above  the  present 
flood-plain  in  the  mid-course  of  the  valley,  it  withdrew  and  erosion 
cut  away  the  valley  train  till  all  that  remained  were  the  terrace 
remnants  on  rock  benches  along  the  sides  of  the  valley.  It  is  not 
known  how  deeply  this  erosion  progressed,  but  probably  the  valley 
was  largely  re-excavated. 

At  some  time  after  this  first  valley  train  was  built  and  before 
the  next  glacial  advance,  the  eastern  end  of  the  region  was  depressed 
relative  to  the  western  end.  A  depression  of  150  to  250  feet  would 
not  have  been  unlikely  and  would  account  for  the  phenomena 
observed. 

The  Kansan  ice  advanced  across  Iowa,  crossed  the  Mississippi 
River  in  the  neighborhood  of  Prairie  du  Chien,  and  projected  a 
tongue  of  ice  into  the  lower  end  of  the  Wisconsin  Valley.  The 
Mississippi  was  dammed,  diverted  into  the  Wisconsin  Valley,  and 
flowed  eastward,  carrying  with  it  not  only  great  quantities  of  coarse 
and  fine  outwash  material,  but  abundant  icebergs  broken  from  the 
ice-front  farther  north  as  it  encroached  upon  the  Mississippi  Valley. 
An  eastward  sloping  valley  train  of  coarse  material  was  built. 
When  the  ice  withdrew,  erosion  cut  away  the  moraine  and  valley 
train,  save  where  remnants  are  left  on  rock  benches  at  Bridgeport 
and  Wauzeka.  The  depth  of  this  erosion  is  not  known  accurately, 


PLEISTOCENE  HISTORY  OF  LOWER  WISCONSIN  RIVER   689 

but  the  valley  was  probably  again  re-excavated  to  about  its  maxi- 
mum depth. 

There  are  no  terraces  in  the  valley  which  correspond  in  age  to 
the  Illinoian  drift  found  at  the  eastern  end  of  the  region,  so  the 
assumption  is  that  the  outwash  from  this  glacial  advance  did  not 
fill  the  valley  high  enough  to  be  above  the  present  surface  of  the 
river.  The  evidence  of  five  well  records1  shows  that  at  one  time  the 
valley  floor  stood,  in  the  main  and  also  the  tributary  valleys,  30 
to  50  feet  below  its  present  level  long  enough  to  accumulate  a  bed 
of  peat.  It  is  probable  that  the  outwash  from  the  Illinoian  invasion 
filled  the  valley  only  to  this  level,  30  to  50  feet  below  the  present 
surface.  Then  ensued  a  period  during  which  the  vegetation  accu- 
mulated on  the  swampy  surface  of  this  outwash. 

During  the  lowan  epoch  loess  was  blown  on  to  the  western  part 
of  the  area,  burying  the  drift  with  a  blanket  of  eolian  material. 

In  Wisconsin  time  not  only  the  moraine  at  Prairie  du  Sac,  but 
the  valley  train  in  the  Wisconsin  Valley,  was  deposited.  As  the 
ice  withdrew  east  of  the  divide  near  Portage,  ponding  produced  a 
lake  which  drained  westward  down  the  drift-filled  Wisconsin 
Valley.  This  was  for  a  time  the  main  drainage  for  at  least  a  hundred 
miles  of  ice-front  lying  toward  the  north,  consequently  a  large  quan- 
tity of  clear  water  flowed  down  the  valley.  The  upper  part  of  the 
fill  was  largely  cut  away,  leaving  remnants  which  now  constitute 
the  upper  terrace  in  the  Wisconsin  Valley.  The  down-cutting 
river  reached  grade  at  the  level  of  the  top  of  the  lower  terrace. 

After  the  ice  had  withdrawn  and  the  glacial  lake  was  drained, 
the  postglacial  Wisconsin  River  cut  away  large  parts  of  the  lower 
terrace  to  form  its  present  flood-plain. 

1  Well  records  which  show  peat  30  to  50  feet  below  the  surface;  fair  grounds  at 
Richland  Center;  schoolhouse  i|  miles  northeast  Richland  Center;  Bear  Creek  £  mile 
north  of  junction  with  Little  Bear  Creek;  Little  Bear  Creek  £  mile  north  of  junction 
with  Bear  Creek  mile  southwest  of  Leland. 


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